Questions tagged [beam]

Questions about the theory and applications of structural elements designed to resist bending.

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2answers
53 views

Can you use an accelerometer to measure beam deflection under static loading?

With an appropriately collocated accelerometer is it possible to retrieve lateral deflection of a beam under static loading. The beam will be loaded and then deflect until it reaches equilibrium with ...
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4answers
76 views

Swing safety: maximum load of beam (supported at one end, free with load on the other)

My husband and his dad built a fort for our two boys. Coming off of one side of the fort is a 4x6 wooden beam with a tire swing attached at the end. It is supported on one side by the fort, but not ...
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1answer
39 views

How to plot bending moment diagram from shear force diagram

With conventions that I adopted shown below I drew roughly the shear force and bending moment diagram of a simply supported beam with concentrated load at the middle. Now while drawing I drew both ...
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1answer
38 views

Optimal placement of two support points along a wooden beam

Assuming a beam that is supported at 2 points as per attached image, what would be Lc (length center) and Lo (length overhang) for maximum strength. (or load bearing capability) For actual material ...
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1answer
35 views

Estimation of Beam Displacement from Acceleration

Hi Engineering Exchange, I have a beam with pinned-pinned boundary conditions (free to rotate but not free to translate). A legacy computer analysis provided me with the maximum mid-span acceleration ...
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7answers
3k views

Is it structurally sound to cut an I beam to a T on one end?

I'd like to confirm whether the replaced beam in the attached picture is structurally sound given the end was cut to a T instead of an I. I had a qualified structural engineer approve the work but I'm ...
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1answer
91 views

Beam for shop gantry

I have a small machine shop and need to size a beam for a gantry crane. The design is a 4 post fixed design with 2 horizontal beams running parallel across the shop ends with 1 beam to be mounted ...
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2answers
60 views

Beam buckling criterion?

If I have an I beam which I subject to some bending load, how can I calculate when the thinner middle part of the I beam will buckle? I though I could use Euler's critical load formula here, but it's ...
2
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1answer
60 views

Limits of Euler-Bernoulli Beam Theory for Wide Plate in Flexure?

I'm looking for established limits or rules of thumb for the validity/accuracy of Euler-Bernoulli beam equations for particularly wide "beams". For example, a simply supported rectangular ...
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1answer
22 views

Moment Arm: What dia.(3“ or 4”) Alum pole 10ft long (thickness .125) will support a load 200 or 300lb pulling at 90 degrees at the end of the pole?

I am trying to determine which diameter (3" or 4") metal pole I need to support a 20ft x 20ft pool shade tarp. I can use either steel or aluminum (aluminum preferred). The wall thickness ...
4
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1answer
43 views

Torsion and Bending stress calculated from deflection

I need help to check a calculation I did. I want to know if it is possible to use this method or if I am using an assumption which is wrong. Let me explain the problem, a beam with length $l$ is ...
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1answer
36 views

simply supported beam with a midspan load

First off non-engineer apologies, A plate of 5251 Aluminium is used to support the load of a centrally seated human I estimate a load of 1 kilonewton. The beam measures a length of 1000mm, 100mm wide. ...
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1answer
25 views

Deflection of a cantilever beam composed of separate (not bonded) planks Uniform load

This is related to this question It is the case of a simple cantilever beam having a uniform rectangular cross-section. cantilever beam composed of separate planks - taken from The question in the ...
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1answer
61 views

What is the difference between W, S, I, H sections?

W and H sections look pretty much the same. S and I sections have their flanges rounded. What difference does this rounding make, why would an S-section be used instead of W-section for example?
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1answer
31 views

How to choose the dimensions for a prestressed I-beam?

I need to design a simply supported symmetric I-beam (for a school problem). However, I can't find much information about the selection of the section or if there exist any standards for that. the ...
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1answer
34 views

steel beam type and size for a clothesline

I have four posts in a square formation. Posts are also square. I want to bolt a beam between two posts on the left and a beam between two posts on the right, and than run some wire between the beams. ...
2
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2answers
67 views

Do the floorboards in timber beam floors have a structural function?

Timber beam floors with perpendicular timber floorboards as indicated in the drawing below are common throughout northern Europe. The floorboards are nailed onto the beams and are quite substantial ...
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1answer
22 views

Centroid of unsymetric bending in T-section

Can anyone please explain how this 24 is coming while calculating the x-cordinate of the centroid.
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2answers
103 views

Maximum induced bending stress within the beam

The Maximum induced bending stress within the beam. Given that: $$\frac{My}{I}$$ The beam depth is 300mm, the width is 150mm. The beam is an I section beam with a 5mm wall thickness. My ...
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1answer
50 views

RHS beam deflection with support on one end

A 1400 mm long galv steel beam, size 40x20x2. 80 mm of the beam on one end is welded in flat position to a platform. How much weight can I put safely on the other end? What if instead of being flat ...
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0answers
20 views

Pin connection on beam - FEA analysis

I am establishing a MatLab FEA code for determining the stiffness of a structure. Diagram of the structure is added below. I have established a code for determining the stiffness of the structure, but ...
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2answers
55 views

Boundary conditions for this beam deflection problem

consider the diagram above. I know that deflection is described by the equation $$EI\frac{d^4y}{dx^4}=p(x)$$ where $L$ is the length of the beam, $E$ is the Young's module, $I$ is the moment of ...
3
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2answers
430 views

Degrees of freedom of an internal hinge in plane beam?

What are the degrees of freedom of an internal hinge in a plane beam? I understand that the bending moment=0, does this mean there is no slope either? Or does it have both degrees of freedom of ...
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0answers
36 views

Sign convention for deflection and slope of beam?

What is the sign convention for deflection and slope of a beam as shown in the diagram below? When I derive the formula using Euler-Bernoulli for deflection and slope myself, I end up with - ...
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1answer
56 views

Why is there a row of circular holes in this concrete beam?

The reinforced concrete beam (approximate dimensions 36" x 18") shown in the image below has a row of circular holes at 3/5ths of the height of the cross-section at approximately 300 mm centres. My ...
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1answer
27 views

Shear flow for unequal leg channel

How does the sine part i.e. $\dfrac{\ell\sin(\theta)}{2}$ appear in the calculation of shear flow ($q$)? I mean, if I'm not mistaken, the sine part is the distance from the x-axis to point D, but how ...
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2answers
34 views

Dimensioning of beam pressed by screw in assembly

I need help dimensioning a screw-beam system of a press. I built one prototype but the beam is bending too much. Below is a sketch of my press. In the middle it has a fixing screw which presses ...
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2answers
56 views

Bending moment in Euler-Bernoulli finite Element

I'm trying to calculate the bending moment distribution on a fixed-fixed Euler-Bernoulli beam. It is known that interelement nodes show different values for the bending moment. What is customary to do ...
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2answers
58 views

What is the strongest way to fasten 8020 extrusions in this arrangement?

I am making a project using 10mm aluminum extrusions. I am trying to connect all three extrusions like the picture below shows and I am going to make my own bracket (in red) out of aluminum since the ...
2
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1answer
63 views

Twist “buckling” critical load

I have a very long beam which is subjected to a torque (I have the moments and shear forces with respect to X along the beam). I can calculate the critical load when the beam would bend if it was ...
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2answers
50 views

Deflection and stress in a freely rotating beam

How do I calculate the deflection and stress of a beam that is rotating freely (for example in space) when a moment is being applied to it, for example by rocket motors at the ends of the beam?
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1answer
329 views

Problem while solving for the moment of a cantilever beam

As in the first image, Moment at any point between C and B should be 0. But when I try to solve it by substituting equal and opposite forces at end C so that anti-clockwise moment of $F(l-a)$ and ...
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0answers
228 views

Problem with cantilever beam and yield strength

Hey, I make a project in which I use a cantilever beam with distributed equal load across the whole beam and I'm using the formulas above to calculate the displacement, moment... My specifications ...
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1answer
66 views

Maximum I-beam girder S12x31.8 span

Does 200lb/in of load on a S12x31.8 over 15 feet seem reasonable? I'm having a tough time trusting the numbers. Two story house with an attic as below. Dotted lines show load bearing walls W1 and W2. ...
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3answers
301 views

Buckling vs. Yielding Failure of Columns

As I have been working through examples of construction projects, I've noticed that in nearly every case of a structural column (sample size considers only homogeneous material columns, no composite ...
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1answer
44 views

What criteria must apply for torsional effects on this beam to be ignored in calcs?

I'm interested in how to work out whether torsional effects can be ignored or not, in calculating the adequacy of a given steel beam in the following idealised eccentric scenario. Or, equivalently, ...
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1answer
77 views

Modification of Beam Equation for Thin Sheet

I am trying to determine the modulus of elasticity (Young's Modulus) for a rigid paper sheet. The issue I am having is that my results for the Young's Modulus change depending on what orientation (...
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2answers
105 views

Pin joint system displacement question

A pinned system comprising bars of the same material and cross-sectional area is subjected to a vertical load P. I am required to form a relationship between FAB and P. The first part of the ...
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0answers
31 views

How to write the equilibrium stress equations for a hollow, rectangular beam?

I have a system consisting of a hollow, rectangular cantilever beam (pictured below). I'd like to write the equilibrium stress equations à la the Cauchy Stress notation. How do I account for the ...
2
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1answer
65 views

Why are variations zero on the endpoints of a beam?

On Wikipedia derivation on Timoshenko beam equation we arrive at this: $$ \delta U = \int_L \left[-M_{xx}\frac{\partial (\delta\varphi)}{\partial x} + Q_{x}\left(-\delta\varphi + \frac{\partial (\...
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2answers
158 views

How to analyze a bent beam: Stress concentration?

I am analyzing a beam, that has a bend in it. Intuitively and inspecting FEA results using a linear solver, there is a stress concentration at the bend of this I-beam. The part was not a straight I-...
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1answer
299 views

Calculating area moment of inertia for a beam with underslung plate?

In a number of designs, a beam will have an underslung welded plate attached, as shown below: In this sketch, a symmetrical standard steel beam/column of dimensions H1 x B1, with web and flange ...
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0answers
55 views

Rotational bending in Timoshenko beam theory

The Wikipedia article on Timoshenko beam theory says: The model takes into account shear deformation and rotational bending effects, I am familiar with shear deformation, but what is meant by "...
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1answer
102 views

simple supported Beam deflection question involving two point loads and a UDL

so i was given a problem by my mechanical principles teacher to work out the max vertical deflection of a simply supported beam with two point loads one a distance of 5.3 away from A and another 5.9 ...
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1answer
462 views

Along which direction is the area moment of inertia taken in bending moment equation?

Is it in the same direction of the applied load or in the co-planar perpendicular direction to the load applied?
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1answer
140 views

MSC Nastran - BAR3/4 elements - can't assign any properties

I'm modeling a pipe in Patran, and I'd like to try bar3 and bar4 elements. I assing the properties CBEAM to my geometry, but when I create the mesh, Patran tell me bar3 and bar4 don't support that ...
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3answers
88 views

Do internal / external stresses affect modal frequency?

Imagine a cantilevered beam, fixed on one end and with a tension line connecting the other end to ground (e.g. perpendicular to the length of the beam). If I increase the tension, does the modal ...
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3answers
169 views

Composite beam- increase in bending moment due to reinforced steel

While trying to solve this question and using the flexure formulas of bending for composite beams I obtained a lower value of moment for steel than for aluminum.How is that possible?
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3answers
104 views

Reaction Forces on a Beam

I'm new to beams and I'm struggling to find the correct vertical reactions forces at support C and E. The correct answer is 8.58 kN for $V_c$ and -3.58 kN for $V_e$ However, when I ...
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2answers
112 views

How to get the bending moment for tie member?

How to get the bending moment for tie member? For the tie member, there is no uniformly distributed load and concentrated load, right? How to get the bending moment? The tension force was found to be ...